The Americans with Disabilities Act (ADA): Accessibility Guidelines for Buildings and Facilities sets the requirements for the use of detectable warnings at curb ramps, walking surfaces, transit platforms and the like to warn visually impaired people of hazards. The Guidelines require that detectable warnings “shall consist of raised truncated domes with a diameter of nominal 0.9 in. (23 mm), a height of nominal 0.2 in. (5 mm) and a center-to-center spacing of nominal 2.35 in. (60 mm) and shall contrast visually with adjoining surfaces, either light on dark or dark on light. The material used to provide contrast shall be an integral part of the walking surface. Detectable warnings used on interior surfaces are required to differ from adjoining surfaces in resiliency or sound-on-cane contact.” § 4.29.2. “Platform edges bordering a drop off and not protected by screens or guard rails shall have a detectable warning . . . 24 inches wide running the full length of the platform drop off” § 10.3.1(8). “If a walk crosses or adjoins a vehicular way, and the walking surfaces are not separated by curbs, railings or other elements between the pedestrian areas and the vehicular areas, the boundary between such areas shall be defined by a continuous detectable warning which is 36 in. (915 mm) wide”. § 4.29.5. Curb ramps are also required to have detectable warnings extending the full width and depth of the curb ramp. See § 4.7.7.
Various tactile tiles having raised truncated domes in compliance with the ADA Guidelines or the equivalent have been developed. These tactile tiles are designed to be glued or mechanically fastened to the existing walking surface or embedded in freshly poured concrete or other settable medium. The truncated domes of these tiles are typically integrated with the tiles such that the domes are a permanent part of the tile.
In some circumstances, areas of the tactile tiles are subjected to frequent and repeated impact such that the truncated domes become chipped or otherwise damaged. In one example, the passenger floor of rail transit cars may be at a different elevation than a passenger platform onto which passengers disembark from the rail car. In other words, pedestrian passengers are required to step up or down to enter or leave the rail car. To accommodate wheelchair ingress/egress, a deployable platform ramp attached to the rail car provides access between the rail car and the different height of the passenger platform. When the ramp is deployed at a rail station onto ADA Guidelines-compliant detectable warnings (or their equivalents), the ramp may impact the truncated domes thereof at a particular distance from the rail car with sufficient force to immediately, or over time, damage the truncated domes in the tile area impacted by the ramp.
Tactile tiles are typically attached to a substrate in a manner, such as mentioned above, which makes removal prohibitively expensive or time intensive. Moreover, the manner of installation and/or dimensions of tactile tiles hinder the replacement of smaller tile portions that may be damaged or for which replacement may otherwise be desirable.
Furthermore, existing detectable warning tiles do not provide or accommodate sensors, lighting, message presentation, electrical or fluid paths, or access to connections for any of these which may exist in adjoining tiles.